When Texas Instruments introduced its TMS320C82 offers a breakthrough in DSP price/performance for a variety of applications, with performance rivaling the 'C80 in certain cases. Targeted applications include video games with 3-D virtual reality graphics, computer-based videophones and videoconferencing, TV settop boxes with a variety of entertainment functions, and digital switching for high-speed telecommunications equipment.
TI's latest DSP solution* integrates on the same silicon two advanced DSPs, along with a reduced instruction set computing (RISC) master processor (MP) for high-speed instruction and parallel data processing. Instruction cache memory for each DSP has been doubled to four Kbytes from the 'C80 architecture, and the amount of data RAM for each DSP has been increased from eight to 12 Kbytes. A simplified external interface allows TI to offer the 'C82 in a 240-pin plastic quad flat pack (PQFP) for surface mount volume production, saving cost and space over the 304-pin grid array (PGA) used by the 'C80.
Each of the 'C82's DSPs has 64-bit instruction words to define more parallel operations and more capable data paths than on other DSPs. With its two powerful DSPs and RISC processor, the 'C82 will generally outperform six to 10 of today's 16-bit DSPs at typical signal processing applications. It would take 10 to 15 typical DSPs and general-purpose microprocessors to equal the 'C82's performance in targeted imaging and video applications.
Some applications needing very high processing performance, such as image processing, network switching and full-room videoconferencing, still need the extra power offered by the 'C80's four on-chip DSPs. However, for applications that do not need the full computational capability of the 'C80, such as 3-D graphics, desktop videoconferencing and videophones, the 'C82 can offer the same performance as the 'C80 at a significantly lower price.
With a production-quantity price of $82 planned in 1996, the 'C82 has been optimized for three groups of applications: digital switching for high-speed telecommunications in multichannel T1, E1 and ATM switches; video games and other uses of 3-D virtual reality graphics; and desktop videoconferencing systems.
For digital switching and other traditional DSP applications, the 'C82 performs as a high-performance general-purpose DSP. In digital switching systems in particular, the key design challenge is often to save space in order to pack the largest possible number of channels into the smallest possible space.
The 'C82 saves board space by consolidating multiple processors into a single chip. This consolidation includes memory and interface chips, as well as the processors themselves, so that the 'C82 replaces many different devices with one. With the space saved by this consolidation, original equipment manufacturers (OEMs) can put more switched channels on the same board, and thus more channels in the same box. In addition, fewer devices require less power to operate and generate less heat, saving space in the box devoted to cooling. All these factors reduce costs as well as space.
Another important source of cost savings is the 'C82's on-chip cache memory. Because this memory is on-chip, there is no need for external, high-cost SRAM to support each DSP. Instead, the system's memory uses DRAM, with its much lower cost per bit, reducing overall component costs.
For video games and 3-D virtual reality graphics, saving board space and reducing chip counts are still important design goals, but the overriding requirement is offering higher-quality graphics while keeping total system costs low. For this reason, existing game systems start out with single-processor architectures capable of producing inexpensive low-end graphics, then add co-processors to achieve higher quality. Game systems based on the 'C82 can offer far superior graphics capabilities at prices competitive to existing systems without the expensive add-ons.
Since the 'C82 consolidates several processors in one chip, it offers higher performance in several areas required by high-end graphics programs. The RISC MP serves as a powerful central processing unit for handling program instructions in real time. The floating-point unit provides workstation-class performance of 100 million floating-point operations per second (MFLOPS) for the non-integer calculations necessary for 3-D object transformations. It also performs the display list processing necessary to transfer pixel renderings to the DSPs efficiently.
The two DSPs handle high-definition pixel renderings for high-resolution 3-D animation in real time. They also perform shaded graphics and texture mapping to provide greater visual detail. And the transfer controller provides high-speed exchange between the very fast on-chip memory and low-cost DRAM. In addition, it can independently perform the two-dimensional bit block transfers that are also necessary for real-time animation. (In graphics terms, the transfer controller acts as a bit block translator.)
These combined processing functions enable new software uses not available previously in affordable systems, such as projecting photographs and even video into 3-D virtual worlds. In addition to 3-D graphics, the 'C82 will also bring about the capability to decode compressed video images, including those complying with the MPEG standards.
As a single-chip implementation, the 'C82 provides the highest-quality, most cost-competitive videoconferencing solution available. Most competing solutions require two or more chips to deliver significantly less performance. By designing with the 'C82, OEMs will be able to bring to market desktop videoconferencing systems for less than $500 -- a price that leading PC OEMs claim will create a volume market for desktop videoconferencing.
While competing solutions are dedicated to a single type of system, the 'C82 is unique in the degree of its programmability and is therefore highly versatile. For videoconferencing, the device will be supported by high-quality implementations of the internationally recognized h.320 and h.324 standards, as well as other standards. In addition, a single 'C82-based system can add or accelerate multimedia functions as diverse as 3-D graphics for virtual reality, MPEG video playback, image processing acceleration for applications such as Photoshop™ and PostScript™, voice recognition, and document image processing that includes high-speed character recognition.
The 'C82 can also be reprogrammed to support new standards as they evolve. This capability is vital to OEMs because videoconferencing is an evolving technology. The standards use adaptive compression methods, and developers are still learning how to generate the best video quality within the standards as they exist today. OEMs cannot afford to be locked into a design that may become obsolete quickly as new techniques are developed. The 'C82 lets them keep up to date with the market without expensive hardware redesign, while maintaining system-level costs at parity with designs based on conventional chip sets.
The 'C82 also helps OEMs improve the quality of their products. The videoconferencing standards establish a baseline but are not in themselves a guarantee of high-quality presentation. In the market race to improve picture and sound resolution and eliminate noise, OEMs often introduce their own programmed enhancements. The programmability of the 'C82 encourages OEMs to make these enhancements, giving them an easy way to improve and differentiate their products in the market.
One of the most common types of electronic equipment for consumers is the settop box. Games, videoconferencing and video decompression for digital broadcast, cable and compact disc playback are applications that can be expected from the next generation of settop boxes to accompany entertainment systems. Settop boxes can also combine applications, so that, for example, a game player can also play audio/video CDs or serve as a videophone. For settop box systems, the 'C82 has special advantages.
Because of its functional integration, the 'C82 can replace as many as three specialized chip sets with a single chip. The RISC MP replaces an overall system CPU and its support chips. The floating-point unit replaces a dedicated numeric co-processor for 3-D graphics. And the DSPs replace modem, video and audio chips used for signal processing.
Moreover, with its full DSP programmability, the 'C82 supports a wide range of standards used in settop systems: h.320 (including h.261), h.324, JPEG, MPEG1, MPEG2 (both audio and video), fax/modem and other communication standards, and so on.
The 'C82 offers OEMs flexibility at no added cost. The device is cost-competitive with dedicated solutions that offer less performance, as well as less flexibility.
The block diagram (see attached) illustrates the 'C82's flexibility for system designers in a videoconferencing system. Because of its internal SRAM cache, the 'C82 interfaces directly to DRAM without degrading performance. The 'C82's simplified system interface allows a PCI bus interface and memory controller to connect the card to the PC system itself and also to the I/O peripherals. These peripherals include an audio codec for a microphone, video capture interface for a camera, and ISDN and/or modem interfaces for telephone line connections.
The phone line connections might be used for 3-D graphics systems to allow users to play interactively at remote locations. The microphone and camera interfaces would probably not be used in digital switching systems. Otherwise, the block diagram would look very similar for these types of systems, too, since the 'C82 integrates many of the support chips used in a variety of designs.
The 'C82 has broken through a price/performance barrier that will enable new high-performance, high-volume applications. With its high performance, consolidation, low cost and programmability, the 'C82 brings the much needed flexibility to the design of applications such as telecommunications switches, 3-D virtual reality graphics and videoconferencing. New levels of performance at affordable prices will soon be available in these applications, enabled by TI's TMS320C82 DSP.
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*DSP Solution Definition: a digital signal processing solution is a combination of DSPs, mixed-signal and complementary ICs, development tools, system software and support. This allows customers to create new products faster and with lower system costs.
Trademarks:
Photoshop and PostScript are trademarks of Adobe Systems Incorporated.
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